MOTIVATION - Ischemic stroke is a common and often devastating condition that continues to be a leading cause of death and disability worldwide. Successful treatment will have a great impact on stroke morbidity and will reduce the socio-economic burden associated with this debilitating disease. Considerable data are now available indicating that MR-based DWI, PWI, and MRA are useful for identifying subgroups of patients who are particularly likely to benefit from, rather than be harmed by, reperfusion therapy. The advancement of multi-detector CT (MDCT) has also improved the diagnostic evaluation of acute stroke patients and a comparative evaluation of optimal exams from both modalities is timely. AIMS - This project has a technology development arm in which MRI methods for DWI, PWI and CE- MRA are improved further, and a clinical arm in which these methods are evaluated in acute stroke patients and MRI's diagnostic sensitivity and specificity as well as clinical yield is compared with the best available MDCT methods (CT, CTP, CTA). METHODS - Parallel imaging will be a major theme of this project. Specifically, acquisition and fast reconstruction methods for spiral, PROPELLER, and Cartesian data will be improved. DWI and PWI methods will be developed to improve quantitation while simultaneously reducing geometric distortions and motion artifacts and significantly improving spatial resolution. New contrast-enhanced MRA acquisition schemes and reconstruction methods will be developed. The development of DWI, PWI, and CE-MRA will be followed by extensive phantom and volunteer studies to assess the image quality. The diagnostic sensitivity and specificity as well as the clinical yield of these optimized MR methods will be compared in 120 consecutive acute stroke patients (within 6-i2hrs after onset of symptoms) with the most optimal perfusion and angiographic methods afforded by a 64-channel MDCT. SIGNIFICANCE - The success of this research effort will serve to significantly improve multi-coil parallel imaging acquisition and reconstruction methods. Clinically, we anticipate that this prospective study will provide a better understanding of the diagnostic capability of both MRI and MDCT for imaging acute stroke patients. Moreover, it will provide tools to help identify patients who will benefit from reperfusion therapies and to exclude patients who are at high risk for reperfusion-related brain hemorrhage.